In general, a photographic processing solution for a silver halide photographic light-sensitive material is prepared for use by measuring and mixing many kinds of necessary components before using or it is an already-prepared photographic processing solution in which the necessary components are mixed in advance in the amounts needed.
A powder type processing agent and a solution type processing agent are known as photographic processing agents. A powder type processing agent is dissolved in a prescribed amount of water before use. In the case of a solution type processing agent, a concentrated solution is usually diluted with a fixed amount of water before use and a non-concentrated solution is used as it is without dilution with water. A ready-prepared photographic processing agent has various advantages since less fluctuation in the quality of a processing solution occurs in its direct use and it can be readily used. Meanwhile, it contains many substances which readily react with each other by an oxidation-reduction reaction and therefore, it is usually separated into one or two kinds of components, which are packaged in a kit form, (hereinafter called a Part) and these components are dissolved in a prescribed amount of water before use.
In recent years, in order to prevent processing solutions from deteriorating during processing, a replenishing treatment is used for the purpose of replenishing the components used up wherein a fixed amount of a replenishing solution per processed unit area of the photographic material is supplied to a processing bath. In this case, the replenishing solution is usually supplied by an automatic supplying pump, where the replenishing solution prepared by dissolving the foregoing packaged part is pumped to a replenishing tank and is automatically supplied therefrom.
The photographic processing agent in which the above parts are packaged in kit form is dissolved, diluted, mixed and then adjusted to a prescribed amount for use as the replenishing solution for color development. However, this photographic processing agent has the following problem: that is, the reducing agent present in the photographic processing agent, for example, a developing agent, is quite unstable in a solution even if it is separately packaged in a kit as a part and this tendency is particularly notable for a p-phenylenediamine type color developing agent.
Methods for stabilizing a liquid kit part containing a p-phenylenediamine type color developing agent are described in, for example, JP-B-45-37957 (the term "JP-B" as used herein means an examined Japanese patent publication), in which a prescribed amount of sulfite is added to an acidic aqueous solution containing the p-phenylenediamine color developing agent; U.S. Pat. No. 3,574,619, in which benzyl alcohol, ethylene glycol and sulfite are added to an acidic aqueous solution containing the p-phenylenediamine color developing agent; and JP-B-55-21084 and JP-B-1-46866, in which sulfite is added to a solution prepared by dissolving the p-phenylenediamine color developing agent in an organic solvent. However, in these conventional methods, the sulfite is rapidly decomposed and sulfur dioxide is generated, which is disadvantageous in a working environment, and in addition, the decomposition of the color development agent rapidly goes on when the concentration of the sulfite is markedly lowered.
Means for solving the problems of rapid decomposition of sulfite and the lack of stability of a developing agent include the method described in, for example, JP-A-51-26543 (the term "JP-A" as used herein means an unexamined published Japanese patent application), in which p-phenylenediamine phosphate is used in place of the sulfite to achieve developing solution stability, JP-A-47-24323, in which the solution containing a p-phenylenediamine color developing agent and sulfite in a fixed amount are sealed in a vessel of a polymer material having a low air permeation coefficient; and further, JP-A-59-210439, in which the pH of the solution containing an N-hydroxyalkyl-substituted p-phenylenediamine color developing agent and sulfite is adjusted to 6 to 8 to achieve developing solution stability.
However, satisfactory stability has not yet been achieved with these prior art techniques since the decomposition goes on slowly even if the developing solution is stored in a sufficiently tightly closed vessel and decomposition of the sulfite is expedited after the vessel is opened and the developing solution is exposed to air.
Further, the dissolution of a color developing agent in preparing a developing solution is not sufficiently improved. Especially, the method described in JP-A-59-210439 has a problem in that a condensed part can not be prepared because of the lower solubility of a color developing agent.
Also, the amount of a developing agent dissolvable is lower in a solution of higher pH, in which a preservative and an alkaline component are present, than in a solution of neutral or lower pH, and it is difficult to increase the concentration of the solution. Consequently, where a lot of the developing solution has to be replenished, the replenishing amount has to be increased, and this results in an increase in the amount of over-flowing waste from a developing solution bath.
Because of the complexity in processing a photographic processing waste to render it non-hazardous and an environmentally acceptable photographic processing waste, in recent years a decrease in developing waste in the photographic processing or elimination of the waste has been required. To meet this requirement, one could consider increasing the concentration of the developing agent in the replenishing solution for development to decrease the replenishing amount so that the developing solution does not over flow. However, even if increasing the concentration of the developing agent in the replenishing solution for development is attempted, it is difficult to increase the amount of the developing agent which will dissolve where high pH components such as alkaline components are present in the replenishing solution for development.
In order to achieve a higher concentration of the developing agent in the developing solution as well as storage stability, usually a packaging form consisting of a part containing a concentrated solution of the color developing agent and the sulfite or the color developing agent, the sulfite and a chelating agent, and a part containing the concentrated solution of the alkaline components are used, wherein the former part is acidified (low pH) and has the function of increasing the solubility. These concentrated solutions are particularly needed for lower replenishment and/or the preparation of a high activity developing solution.
However, it has been found that while the solubility of the developing agent is increased at a pH of 6 or higher, there is the tendency for the sulfite compound to decompose and generate sulfur dioxide and the developing agent is degraded. Therefore, this type of packaging form is not preferable especially for long storage. More specifically, when the replenishment was carried out after long storage, the minimum density (D.sub.min) of the photographic image is increased and the sensitivity is decreased as the developing agent is degraded.
Further, the use of a large amount of sulfite depresses the color developing reaction since an oxidation product of the developing agent is captured. Especially when a silver halide color photographic light-sensitive material with a high content of silver chloride is subjected to color development, the density of the color image is markedly reduced because of the dissolution of silver chloride by the sulfite. Therefore, it is not preferable to add sulfite in an amount sufficient to provide storage over a long period of time.
Meanwhile, with respect to the stability of the developing agent itself, it is reported in The Journal of Photographic Science, vol. 31, pp. 177 to 180 (1983) that in the condition of low pH, the formation of a small amount of an oxidation product of the developing agent lowers the stability of the developing solution due to rapid hydrolysis (deamination) of the oxidation product of the developing agent, which takes place following the oxidation reaction of the developing agent.
Further, it is difficult to maintain developing solution stability over a long period of time at a pH of 7 or lower, especially under conditions of exposure to air, even using antioxidation agents other than sulfite (JP-A-63-30644, JP-A-60-106564 and JP-A-59-210439).